In recent years, with capacity increase of hard disks and the like in computer devices, the recording density of information in single recording surfaces is increasing. For example, in order to increase the recording capacity per unit area of a magnetic disk, it is necessary to increase the surface recording density. However, as the recording density increases, the occupying recording area per one bit on a recording medium becomes reduced. If this bit size becomes reduced, since the energy that one bit information has becomes close to the thermal energy of room temperature, problems of heat demagnetization such as recorded information is inversed or diminished due to the thermal fluctuation occur.
The in-plane recording type that has been generally used is a magnetic recording type such that the direction of magnetization is directed to the in-plane direction of the recording medium. However, in this type, disappearance of recorded information by the above-mentioned heat demagnetization, and the like easily occur. Consequently, in order to solve such problems, the in-plane recording type is in a transition to the vertical recording type in which the magnetization signal is recorded in a direction perpendicular to the recording medium. In this recording type, magnetic information is recorded in a principle of moving single magnetization closer to the recording medium. According to this type, the recording magnetic field is nearly directed to the vertical direction with respect to the recording film. The information recorded with the vertical magnetic field keeps energetic stability easily since the N pole and the S pole hardly make a loop in the surface of the recording film. Therefore, this vertical recording type is strong against heat demagnetization in comparison to the in-plane recording type.
However, in recent years, there has been demand for the recording medium to have higher density in response to the need to perform recording/reproduction of larger and higher density information. Therefore, in order to suppress the influence between adjacent domains or thermal fluctuation to a minimum, a recording medium having strong coercivity has started to be adopted. Therefore, also with above-described vertical recording type, it has been difficult to record information on a recording medium.
Consequently, in order to solve this problem, a hybrid magnetic recording type (the near-field light assist magnetic record type) is provided in which the domain is locally heated by the near-field light to reduce coercivity temporarily, and writing is performed in the meantime. This hybrid magnetic recording type uses the near-field light that is generated by the near-field light generating element formed in the near-field light head. With use of this near-field light generating element, it becomes possible to handle optical information in a region that becomes equal to or less than the light wavelength, which has been the limit in conventional optical systems. Consequently, it is possible to achieve a high density of record bits surpassing conventional light information recording/reproducing devices and the like.
The near-field light generating element is constituted, for example, by an optically tiny opening, which is formed in a size equal to or less than the light wavelength, and surpasses the light diffraction limit, and a projection portion, which is formed in a nanometer size, and the like.
As the record head according to the above-described hybrid magnetic recording type, various types are provided. As one of the types, a near-field light head that tries to increase the recording density by reducing the size of light spots is known (for example, see Patent Documents 1 and 2).
This near-field light head mainly includes: a main magnetic pole; a subsidiary magnetic pole; a coil winding in which a conductor pattern of the screw shape is formed in the inside of an insulator; a metallic scatterer that generates the near-field light from irradiated laser light; a plane laser light source that irradiates the laser light toward the metallic scatterer; and a lens that focuses the irradiated laser light. Each of these components is attached to the lateral side of a slider that is fixed to the apex of the beam.
In the main magnetic pole, one end side thereof is a surface opposite to the recording medium, and the other end side thereof is connected to the subsidiary magnetic pole. That is to say, the main magnetic pole and the subsidiary magnetic pole constitute the single magnetization type vertical head in which one magnetic pole (single magnetization) is disposed in the vertical direction. In addition, the coil winding is fixed to the subsidiary magnetic pole such that a part of the coil winding passes between the magnetic pole and the subsidiary magnetic pole. The magnetic pole, the subsidiary magnetic pole and the coil winding constitute the electromagnet as a whole.
On the apex of the main magnetic pole, the above-mentioned metallic scatterer composed of gold and the like is attached. In addition, the above-mentioned plane laser light source is disposed in a position separated from the metallic scatterer, and the above-mentioned lens is disposed between this plane laser light source and the metallic scatterer.
Each of above-described components is attached in the order of the subsidiary magnetic pole, the coil winding, the main magnetic pole, the metallic scatterer, the lens and the plane laser light source from the lateral side of the slider.
In the case where the near-field light head constituted as described above is used, various types of information are recorded on a recording medium with generation of the near-field light and at the same time application of the recording magnetic field. That is, the laser light is irradiated from the plane laser light source. This laser light is collected by a lens, and irradiated to the metallic scatterer. Then, since inside free electrons are vibrated uniformly by the electric field of the laser light, plasmon is excited and the metallic scatterer generates the near-field light in the apex portion. As a result, the magnetic recording layer of the recording medium is locally heated by the near-field light, and coercivity is reduced temporarily.
In addition, with supply of the drive current to the conductor pattern of the coil winding at the same time as irradiation of the above-mentioned laser light, the recording magnetic field is locally applied with respect to the magnetic recording layer of the recording medium that is close to the main magnetic pole. By this, it is possible to record various types of information on a magnetic recording layer where the coercivity is temporarily reduced. That is to say, by cooperation of the near-field light and the magnetic field, it is possible to perform recording on a recording medium.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2004-158067
[Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2005-4901